Effect of solution composition of plasmid DNA on gene transfection following liver surface administration in mice

ssc-miR-361-3p Suppresses Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Replication and Its In Vivo Expression in Mice

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically devastating diseases affecting the global pig industry. Host microRNAs directly target viral gene regions to exert their disease-fighting effects. PRRS virus (PRRSV) infection upregulates miR-361-3p expression; however, it is unclear whether it can exert inhibitory effects by directly targeting viral genes. Bioinformatic and experimental findings revealed that miR-361-3p inhibited PRRSV replication by directly targeting the PRRSV ORF1b and ORF1a loci. Intramuscular injection of pcDNA3.1-pri-miR-361 verified the expression of miR-361-3p in mammals. In summary, miR-361-3p plays an important role in infection and may be a promising therapeutic target for PRRS, providing insights into possible drug therapies.

Pretreatment with epidermal growth factor enhances naked plasmid DNA transfer onto gastric serosal surface in mice

We have developed a simple administration method, which is gastric serosal surface instillation of naked plasmid DNA (pDNA) in experimental animals. The purpose of this study was to improve gastric gene transfer efficiency by pre-treatment with a macropinocytosis enhancer, such as fetuin or epidermal growth factor (EGF), in mice. A series of concentrations of fetuin were instilled onto gastric serosal surface prior to instillation of naked pDNA in mice; however, fetuin did not improve transgene expression in the stomach 6 h after administration of pDNA. EGF also did not affect transgene expression in the stomach when pDNA was instilled immediately after EGF instillation. On the other hand, when pDNA was instilled onto gastric serosal surface 24 h after EGF treatment, transgene expression in the stomach was significantly improved by 2.6-fold. In addition, transgene-positive cells were increased 5.3-fold by EGF pre-treatment. High transgene expression in the stomach lasted for 48 h in the EGF pre-treatment group in comparison with that in the no pre-treatment group. These findings are valuable to develop an effective method of in vivo gene transfer to the stomach.

Rubbing gastric serosal surface enhances naked plasmid DNA transfer in rats and mice

We have developed in vivo gene transfer to mesothelial cells on the peritoneal organs, including the stomach. Simple instillation of naked plasmid DNA onto the gastric serosal surface in mice resulted in effective but transient transgene expression. Here, we developed a simple method to improve not only the transfection efficiency but also the duration of transgene expression. Rubbing the gastric serosal surface using a medical spoon immediately after instillation of naked plasmid DNA onto the gastric serosal surface resulted in 59-fold higher transgene expression 24 h after administration in rats. Without rubbing, transgene expression decreased under the detection limit 7 d after administration. On the other hand, rubbing the gastric serosal surface with a medical spoon after instillation of plasmid DNA prolonged transgene expression for one month. Mechanistic study in mice revealed that improved transfection should not be due to stimulation of cell function such as macropinocytosis by rubbing because rubbing before instillation of plasmid DNA did not improve transfection. Plasmid DNA should enter effectively into cells during rubbing. These findings are valuable to develop an effective method of in vivo gene transfer into peritoneal organs.

[Organ-, region- and cell-selective gene transfer using non-viral vectors]

Safety in gene therapy is an important issue since both viral and non-viral vectors have toxic side effects. Not only vectors themselves, but also distributions of produced proteins affect safety in gene therapy; thus, development of target-selective gene transfer methods is rational. We have developed organ-, region- and cell-selective gene transfer methods using non-viral vectors. To deliver foreign gene to liver parenchymal cells (hepatocytes), galactosylation of cationic liposome/plasmid DNA complex is useful strategy. Based on analyses for intrahepatic disposition characteristics and interaction with blood components, we formulated novel galactosylated lipoplex with regulated salt concentration to reduce particle size of lipoplex and to stabilize lipoplex simultaneously; as a consequence, we succeeded in improvement of hepatocyte-selective gene transfer after intraportal injection of the lipoplex in mice. On the other hand, administration routes are important for target-selective gene transfer. We discovered that simple instillation of naked plasmid DNA onto organ surface (the liver, kidney, spleen, stomach and lung) in mice and rats could result in effective and region-selective transgene expression. Neither physical force nor carriers are necessary for gene transfer onto organ surface mesothelial cells. To rationally improve transfection efficiency, mechanism of gene transfer should be elucidated. We clarified that Rac-mediated macropinocytosis was required for naked plasmid DNA transfer in gastric mesothelial cells.

[Development of drug delivery system by utilizing absorption from liver surface and its application]

Because it is difficult to achieve local drug activity following administration by the conventional intravenous and oral routes, I sought to develop a new route of administration utilizing drug absorption from the liver surface in order to target that organ. Although direct application to the liver surface should yield local drug distribution, drug absorption from the liver surface has not been reported in the literature. Therefore, we analyzed, as a model, the efficiency of absorption of several organic anions and dextrans of various molecular weights following application to the rat liver surface in vivo using a cylindrical diffusion cell. Each compound appeared gradually in the plasma, followed by excretion into the bile and/or urine, indicating the possibility of drug absorption from the liver surface. The absorption process from the liver surface may not involve a specific transport system because dose and transport inhibitors had no detectable effect. In addition, molecular weight was found to be a determinant of absorption through the liver surface. The efficiency of targeting desired region in the liver was enhanced considerably by application to the liver surface, compared to intravenous administration. Moreover, I have obtained several promising results from the application of this new drug delivery system to anticancer drugs and gene therapy. On the other hand, I have also clarified the characteristics of drug absorption from the surfaces of the kidney, stomach, cecum and small intestine, and plan to apply the physiological findings to other fields.

Spleen-Selective Gene Transfer Following the Administration of Naked Plasmid DNA onto the Spleen Surface in Mice

The purpose of present study was to examine spleen-selective gene transfer following the administration of naked plasmid DNA (pDNA) onto the spleen surface in mice. Gene expression in the spleen and other tissues was evaluated based on firefly luciferase activity. Six hours after spleen surface instillation of naked pDNA, high gene expression in the spleen was observed. On the contrary, intravenous and intraperitoneal administration of naked pDNA resulted in no detectable gene expression. After instilling naked pDNA onto the spleen surface, gene expression in the spleen was significantly higher than those in other tissues. Six hours after instillation of naked pDNA onto the spleen surface, gene expression in the spleen reached the peak value, and thereafter decreased gradually. By utilizing a glass-made diffusion cell that is able to limit the contact dimension between the spleen surface and naked pDNA solution administered, site-specific gene expression in the spleen was found. This novel gene transfer method is expected to be a safe and effective strategy for DNA vaccine against serious infectious diseases and cancers.

Unilateral Lung-Selective Gene Transfer Following the Administration of Naked Plasmid DNA onto the Pulmonary Pleural Surface in Mice

The purpose of the present study was to examine unilateral lung-selective gene transfer following the administration of naked plasmid DNA (pDNA) onto the pulmonary pleural surface in mice. Naked pDNA was administered intravenously, intraperitoneally, and instilled onto the right pulmonary pleural surface. Four hours later, right pulmonary pleural surface instillation of naked pDNA resulted in high gene expression in the right lung. On the contrary, intravenous and intraperitoneal administration of naked pDNA resulted in no detectable gene expression. After instilling naked pDNA onto the right or left pulmonary pleural surface, gene expressions in the applied lung were significantly higher than those in the other lung and tissues. In addition, gene expressions were detected only in the intrathoracic tissues, not in the intraperitoneal tissues. Four hours after instillation of naked pDNA onto the right pulmonary pleural surface, gene expression in the right lung was the highest, and thereafter gene expression in the right lung decreased gradually. This novel gene transfer method is expected to be a safe and effective treatment against serious lung diseases.

Stomach-Selective Gene Transfer Following the Administration of Naked Plasmid DNA onto the Gastric Serosal Surface in Mice

The purpose of the present study was to achieve a stomach-selective gene transfer following the administration of naked plasmid DNA (pDNA) onto the gastric serosal surface in mice. Gene expression in the stomach and other tissues was evaluated by firefly luciferase activity. Six hours after gastric serosal surface instillation of naked pDNA, high gene expression in the stomach was observed. On the contrary, intravenous and intraperitoneal injection of naked pDNA exhibited no detectable gene expression. Following instillation of naked pDNA onto the gastric serosal surface, gene expression in the stomach was significantly higher than in other tissues. Gene expression in the stomach was highest 12 h after the instillation and thereafter decreased gradually. Utilizing a glass-made diffusion cell that is able to limit the contact dimension between the gastric serosal surface and the naked pDNA solution administered, site-specific gene expression in the stomach was achieved. This novel gene transfer method is expected to be a safe and effective treatment against serious stomach diseases.